Re: Parallel downloads

[Tobias Geerinckx-Rice]

Hullo Pierre!

Pierre Neidhardt 写道：
> Is there any plan to support parallel downloads?

Guix already downloads sources and substitutes in parallel with 
other builds/downloads through the --max-jobs option.

You could add a separate knob for downloads that defaults to 
--max-jobs.  Or even (* max-jobs cores).  No plans for that AFAIK. 
I don't think it's a trivial tweak.

I'm interested in the numbers behind this claim:

> Currently downloads are a bottleneck for `guix install / 
> upgrade`,
> parallel downloads could reduce the operation duration by an 
> order
> of magnitude.

…because on a substitute-only workload, my default --max-jobs=4 
connections give me 4 MiB/s versus 1.5 MiB/s on a single job.

That's not even a linear increase, let alone an order of magnitude 
(base 2 doesn't count :-).

Kind regards,

T G-R

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